Several characteristics make human papillomavirus (HPV) amenable to vaccination. Anti-HPV-directed vaccines are based on the observation that HPV E6 and E7 oncoproteins are constitutively expressed in HPV-positive cervical cancer and may serve as tumor rejection antigens. Five HPV types (16, 18, 31, 33, and 45) account for 80% of cervical cancer. Until now, the type of immune response capable of mediating an effective antitumor response has not been defined. In order to define the anticancer-directed immune response in situ, we characterized CD4(+) and CD8(+) sorted T cells from peripheral blood lymphocytes, freshly harvested tumor tissue, and tumor-infiltrating lymphocytes (TIL) from a patient with cervical cancer. The HLA-DR-restricted CD4(+) T-cell receptor VB16-, VA10-, VA21-, and VA22-positive CD4(+) T-cell line derived from TIL recognizes autologous HLA-DR*0402(+) (HPV33(+)) cervical cancer cells, as determined by gamma interferon secretion. Testing of different peptides spanning the E7 gene revealed that the HPV33(73-87) peptide ASDLRTIQQLLMGTV represents the immunodominant epitope which can also be presented by the DR*0401 allele to TIL. Such major histocompatibility complex class II-presented peptides represent attractive candidates to augment T-cell responses directed against autologous tumor cells.